1. Field of the Invention
The present invention relates to a hermetic compressor, and more particularly to an improved bearing engagement structure for a hermetic compressor, which facilitates an assembly/disassembly between a unitary cylinder-frame structure and a journal bearing.
2. Description of the Prior Art
As shown in FIG. 1, a general hermetic compressor includes: a hermetically sealed container 1 having upper and lower shells 1a, 1b; and a motor unit 3 provided in the container 1 and having a stator 3a and a rotor 3b.
A lower end of each of a plurality of support springs 4 is connected at an inner periphery of the lower shell 1b, and an upper end of each of the support springs 4 supports a frame 2.
A crank shaft 5 having an eccentric portion 6 formed at an upper end thereof is heat-fitted into the rotor 3b. A cylinder 7 is connected to an upper portion of the frame 2.
A piston 8 that horizontally shuttles in the cylinder 7 is engaged to the eccentric portion 6 of the crank shaft 5.
A valve plate 9 is attached onto an end portion of the cylinder 7, and a head cover 10 is attached onto the valve plate 9. A suction muffler (not shown) is mounted on a portion of the head cover 10.
With reference to FIG. 2, a conventional cylinder-bearing structure for a hermetic compressor includes the frame 2 having a plurality of holes receiving respective bolts 16 therethrough, and a journal bearing 15 with a plurality of bolt holes (not shown) formed at an upper portion thereof for being engaged through corresponding ones of the frame bolt holes receiving the bolts 16. That is, the frame 2 and the journal bearing 15 are engaged to each other by the plurality of bolts 16.
The composition of a crank shaft and a connecting rod employed with the cylinder-bearing structure will now be described.
As shown in FIG. 3, a sleeve 12 is fixedly inserted within the inner periphery of a big end of a connecting rod 11. A crank shaft pin 3 is inserted into the sleeve 12.
FIG. 4A illustrates a connecting rod formed of two detachable parts 11a, 11b. FIG. 4B shows another type of connecting rod wherein two parts 12a, 12b are engaged to each other by use of engagement members, such as bolts and clips 14.
However, such a conventional cylinder-bearing structure for a hermetic compressor requires a tapping process for forming the engagement holes and a plurality of bolts for fastening the journal bearing 15, thereby disadvantageously increasing the number of parts and the processing steps required.
Also, when the crank shaft and the connecting rod are engaged to the conventional cylinder-bearing structure, there are witnessed several disadvantages as described hereinbelow.
Initially, in the sleeve type cylinder-bearing structure as shown in FIG. 2, because of the use of the sleeve 12, the crank shaft pin 13 should be formed smaller in diameter, thereby weakening the shaft pin 13.
Further, in the case of the detachable connecting rods as shown in FIGS. 3A and 3B, there is required a higher level of precision in the processing steps thereof while demanding otherwise unnecessary additional parts, such as bolts and clips.
Still further, the separable construction of the connecting rod may weaken its strength for transmitting the compression force.